Field of Invention
The present invention relates to a wavelength converted light emitting device.
Description of Related Art
Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
FIG. 1 illustrates an LED described in more detail in U.S. Pat. No. 7,352,011, which is incorporated herein by reference. An LED 10 is mounted on a support structure (not shown in FIG. 1). An inner lens 64 is molded over LED 10. Lens 64 is formed as follows: a mold in the shape of lens 64 is positioned over LED 10. The mold may be lined with a non-stick film. The mold is filled with a suitable transparent heat-curable liquid lens material such as silicone or epoxy. A vacuum seal is created between the periphery of the support structure and the mold, and the two pieces are pressed against each other so that each LED die 10 is inserted into the liquid lens material and the lens material is under compression. The mold is then heated to about 150 degrees centigrade (or other suitable temperature) for a time to harden the lens material. The support structure is then separated from the mold. In a separate molding step (using a mold with deeper and wider indentations) an outer phosphor/silicone shell 66 of any thickness is formed directly over the inner lens 64. An outer lens 68 may be formed over the phosphor/silicone shell 66 using another mold to further shape the beam.